An apparatus and method for growing a bulk single crystal nitride material

Abstract

An apparatus and method for growing nitride bulk single crystal, including an autoclave having a pre-growth zone and a growth zone. With control of the concentration of a saturated solution in a pre-growth chamber, the oversaturation reaction conditions for the overall process of growth of the nitride bulk single crystal can be regulated. By regulating the liquid level difference of the melt on an upper surface of a seed crystal, nucleation growth of N / Ga is preferentially performed on the surface of the seed crystal, which suppresses polycrystal formation at a gas-liquid interface and improves the growth rate of crystal and the utilization rate of raw materials.

Description

BACKGROUND OF THE INVENTION[0001]The invention relates to the field of semiconductor optoelectronic materials, and especially to a novel apparatus and method for bulk nitride single crystal growth with liquid phase epitaxy.[0002]GaN is the third generation of semiconductor material, and due to its features such as broad band gap, high pressure resistance, and high thermal conductivity, GaN has a wide market prospect in the field of high-end GaN-based optoelectronic devices in manufacturing high power LEDs / Ds, high-frequency and high-speed microwave detectors, etc., which has attracted wide attention in the industry.[0003]Since the GaN material is decomposed into gallium and nitrogen under normal pressure and at a temperature of 877° C., the melting of GaN can only be achieved at a high temperature and under high pressure (2220° C., 6 GPa). Free-standing GaN substrate is difficult to obtain using the traditional Czochralski method (also known as the vertical pulling method, Czochrals...

AI Technical Summary

Benefits of technology

[0005]The invention provides a novel autoclave apparatus and a method for growth of bulk GaN, which combines the reaction conditions and principle of dynamics of Na Flux, achieves preferential growth of the crystal nucleus on the surface of a seed crystal in the growth process of nitride, suppresses the formation of polycrystal nitride at the gas-liquid interface, improves the growth rate and the crystal quality of bulk GaN, and efficiently overcomes the defect of the traditional single-chamber autoclave.

Problems solved by technology

Free-standing GaN substrate is difficult to obtain using the traditional Czochralski method (also known as the vertical pulling method, Czochralski process, or CZ method) for preparing a single crystal semiconductor substrate such as silicon and gallium arsenide substrate.

Lattice and thermal stress mismatches between the epitaxial material and the heterogeneous substrate lead to high dislocation density of the epitaxial layer, and affects performance of the device.

HVPE has a fast growth rate and can produce a large-sized single crystal material, but the prepared GaN single crystal has problems such as high dislocation density (˜106 cm−2) and residual stress.

A crystal synthesized by using the ammothermal growth method also has good quality (˜103 cm−2) but a slow crystal growth rate and high requirement of laboratory equipment, which is adverse to industrialized production.

However, the traditional autoclave generally has only one chamber for mixing the raw materials and the seed crystal together and then is directly heated for single crystal growth.

As such, during the period of initial heating-pressurizing and later cooling process, the raw material solution inevitably contacts the surface of the seed crystal when the growth conditions for the single crystal are not met, forming a polycrystal GaN and other intermediate phase products and thus affecting the crystal quality of the material.

At the same time, the GaN polycrystal is formed at the gas-liquid interface, which causes slow growth rate of the crystal and low utilization rate of raw materials, which is an insurmountable defect of the traditional single-chamber autoclave.

Images